Synthesis and some properties of light lanthanide complexes with 4,4′-bipyridine and dibromoacetates
Thermal study
0
A. Czylkowska
0
0
A. Czylkowska (&) Institute of General and Ecological Chemistry, Lodz University of Technology
, Lodz,
Poland
In this study, new complexes with formulae: Ce(4bpy)(CHBr2COO)3 H2O, Ln(4-bpy)0.5(CHBr2COO)3 2H2O (where Ln(III) = Pr, Nd, Sm; 4-bpy = 4,40-bipyridine) and Eu(4-bpy)(CHBr2COO)3 2H2O were prepared, and characterized by chemical and elemental analyses, and IR spectroscopy. The way of metal-ligand coordination was discussed. They are small crystalline. The complexes of Pr(III), Nd(III), and Sm(III) are isostructural in group. Conductivity studies (in methanol, dimethylformamide, and dimethylsulfoxide) were also performed and described. The thermal properties of complexes in the solid state were studied using TG-DTG techniques under dynamic flow of air atmosphere. TG-MS system was used to analyze principal volatile thermal decomposition and fragmentation products evolved during pyrolyses of Ce(III) and Sm(III) complexes in dynamic flow of air atmosphere.
-
This article is a continuation of our earlier research on
lanthanide complexes with 4,40-bipyridine (4-bpy) and
halogenoacetates. The rare earth compounds containing
halogenoacetates have been studied by many authors. They
consider mainly the metalligand coordination and
magnetic behavior. The mixed-ligand complexes of some
lanthanides with 2,20- or 4,40-bipyridine and chloroacetates are
known, but with only scant information concerning their
thermolysis. Several notes of discussed compounds
containing halogenoacetates have been summarized in
[13].
Our resent investigation related to mixed-ligand
lanthanide complexes with 4-bpy and di- or trichloroacetates.
We obtained compounds of general formulae: Ln(4-bpy)n
(CHCl2COO)3 mH2O [1, 2, 47] and Ln(4-bpy)n(CCl3
COO)3 mH2O [1, 3, 8, 9] in series Ln(III) = Y, La ? Lu
(without Pm). They were characterized by elemental
analysis, molar conductivity, and IR spectra. Their
thermal behaviors were also studied. The way of metalligand
coordination was discussed. The chloroacetate groups link
with rare earth elements in many different ways. In case
of La(III) [4] and Sm(III) [5] compounds, dichloroacetate
groups coordinate as chelating tridentate and bridging
ligands, and in other compounds [2] as bidentate chelating
and monodentate ions. In all compounds 4-bpy joins with
lanthanide by one nitrogen atom (only in complexes
Er(III), Tb(III), and Lu(III), also half molecule of 4-bpy
lies in outer coordination sphere [2]). In the literature,
there is not much information about lanthanide complexes
with bipyridine isomers and dibromoaceates. Thermal
studies of compounds with empirical formulae Ln(2-bpy)
(CHBr2COO)3 mH2O where Ln(III) = Nd, Er were
characterized in [10]. In one of our previous articles, we have
described preparation and some behaviors of La(III) and
Y(III) complexes with title ligands [11]. In this work, we
present the synthesis, some physicochemical properties,
and thermal studies of new compounds of light rare earth
elements with 4-bpy and dibromoacetates. These studies
of lanthanide(III) complexes with 4,4-bipyridine and
halogenoacetates allow us to determinate the influence on
the kinds of forming complexes, their properties, and
thermal decomposition dependent on the type of halogen
atoms in carboxylates.
Materials, synthesis, and analysis
4,4-bipyridine, CHBr2COOH, Ln2O3 (where Ln(III) = Nd,
Sm, Eu), Pr6O11, Ce(NO3)3 6H2O, dimethylsulfoxide
(DMSO), dimethylformamide (DMF), and methanol (MeOH)
(anhydrous) p.a. were obtained from Aldrich and Lab-Scan.
Water solutions of metal(III) dibromoacetates were prepared
by adding 2 mol L-1 dibromoacetic acid to freshly
precipitated hydroxides (or freshly precipitated cerium(III)
carbonate) in ca. stoichiometric quantities. (in temperature B18 C,
because lanthanide dibromoacetates in solution are relatively
unstable; in presence of 4-bpy their stability arise).
The mixed-ligand complexes were synthesized by
reaction of freshly obtained solutions of appropriate Ln(III)
dibromoacetaes with solutions of 4-bpy (pH * 5). The
molar ratio of M(III):4-bpy was 1:2. Solution of 4-bpy in
31.3 mL of 96 % v/v ethanol (12.4 mmol) was added to
8.7 mL of water solution of Ln(III) dibromoacetates
(6.2 mmol). The products were washed in 40 % v/v ethanol
and then in ethanol and diethyl ether mixture (1:1). All
compounds were dried in open air. The contents of
metal(III) ions in obtained solutions were mineralized and
determined by EDTA titration.
The carbon, hydrogen, and nitrogen contents in the
prepared complexes were determined using a Carbo-Erba
analyzer with V2O5 as an oxidizing agent.
Methods and instruments
IR spectra were recorded using a NICOLETT 6700
Spectrometer (4000400 cm-1 with accuracy of recording
1 cm-1) using KBr pellets. Molar conductance was
measured on conductivity meter of the OK-102/1 type
equipped with an OK-902 electrode at 25 0.5 C, using
1 9 10-3 mol L-1 solutions of complexes in methanol,
dimethylformamide, a (...truncated)